diff --git a/src/wireviz/wireviz.py b/src/wireviz/wireviz.py
index b08460e..e76d216 100755
--- a/src/wireviz/wireviz.py
+++ b/src/wireviz/wireviz.py
@@ -15,12 +15,13 @@ from wireviz.Harness import Harness
 from wireviz.wv_helper import expand, get_single_key_and_value, is_arrow, open_file_read, smart_file_resolve
 
 
-def parse_text(yaml_str: str, file_out: (str, Path) = None, return_types: (None, str, Tuple[str]) = ('html','png','svg','tsv'), image_paths: List = []) -> Any:
+def parse_text(yaml_str: str, file_out: (str, Path) = None, output_formats: (None, str, Tuple[str]) = ('html','png','svg','tsv'), return_types: (None, str, Tuple[str]) = None, image_paths: List = []) -> Any:
     """
     Parses a YAML input string and does the high-level harness conversion
 
     :param yaml_input: a string containing the YAML input data
     :param file_out:
+    :param output_formats:
     :param return_types: if None, then returns None; if the value is a string, then a
         corresponding data format will be returned; if the value is a tuple of strings,
         then for every valid format in the `return_types` tuple, another return type
@@ -30,14 +31,15 @@ def parse_text(yaml_str: str, file_out: (str, Path) = None, return_types: (None,
          - "harness" - will return the `Harness` instance
     """
     yaml_data = yaml.safe_load(yaml_str)
-    return parse(yaml_data=yaml_data, file_out=file_out, return_types=return_types, image_paths=image_paths)
+    return parse(yaml_data=yaml_data, file_out=file_out, output_formats=output_formats, return_types=return_types, image_paths=image_paths)
 
-def parse(yaml_data: Dict, file_out: (str, Path) = None, return_types: (None, str, Tuple[str]) = ('html','png','svg','tsv'), image_paths: List = []) -> Any:
+def parse(yaml_data: Dict, file_out: (str, Path) = None, output_formats: (None, str, Tuple[str]) = ('html','png','svg','tsv'), return_types: (None, str, Tuple[str]) = None, image_paths: List = []) -> Any:
     """
     Parses a YAML dictionary and does the high-level harness conversion
 
     :param yaml_data: a dictionary containing the YAML data
     :param file_out:
+    :param output_formats:
     :param return_types: if None, then returns None; if the value is a string, then a
         corresponding data format will be returned; if the value is a tuple of strings,
         then for every valid format in the `return_types` tuple, another return type
@@ -276,7 +278,7 @@ def parse(yaml_data: Dict, file_out: (str, Path) = None, return_types: (None, st
             harness.add_bom_item(line)
 
     if file_out is not None:
-        harness.output(filename=file_out, fmt=return_types, view=False)
+        harness.output(filename=file_out, fmt=output_formats, view=False)
 
     if return_types is not None:
         returns = []
diff --git a/src/wireviz/wv_cli.py b/src/wireviz/wv_cli.py
index a87a08b..eb94633 100644
--- a/src/wireviz/wv_cli.py
+++ b/src/wireviz/wv_cli.py
@@ -42,14 +42,14 @@ def wireviz(file, format, prepend, output_file, version):
         filepaths = list(file)
 
     # determine output formats
-    return_types = []
+    output_formats = []
     for code in format:
         if code in format_codes:
-            return_types.append(format_codes[code])
+            output_formats.append(format_codes[code])
         else:
             raise Exception(f'Unknown output format: {code}')
-    return_types = tuple(sorted(set(return_types)))
-    return_types_str = f'[{"|".join(return_types)}]' if len(return_types) > 1 else return_types[0]
+    output_formats = tuple(sorted(set(output_formats)))
+    output_formats_str = f'[{"|".join(output_formats)}]' if len(output_formats) > 1 else output_formats[0]
 
     image_paths = []
     # check prepend file
@@ -75,7 +75,7 @@ def wireviz(file, format, prepend, output_file, version):
         file_out = file.with_suffix('') if not output_file else output_file
 
         print('Input file:  ', file)
-        print('Output file: ', f'{file_out}.{return_types_str}')
+        print('Output file: ', f'{file_out}.{output_formats_str}')
 
         with open_file_read(file) as file_handle:
             yaml_input = file_handle.read()
@@ -83,7 +83,7 @@ def wireviz(file, format, prepend, output_file, version):
 
         yaml_input = prepend_input + yaml_input
 
-        wv.parse_text(yaml_input, file_out=file_out, return_types=return_types, image_paths=[file_dir, prepend_dir])
+        wv.parse_text(yaml_input, file_out=file_out, output_formats=output_formats, image_paths=[file_dir, prepend_dir])
 
     print()